Any playoff loss will not be remembered fondly by the Celtics faithful, but Sunday’s 104-102 loss to the Milwaukee Bucks should be.

Sunday was the day that both Jaylen Brown and Jayson Tatum confirmed their respective status’ as longterm pieces to the Celtics’ championship puzzle. Now - just as much as Kyrie Irving and Gordon Hayward - the “Jay-Team” holds the keys to the next great Boston basketball team.

The 21-year-old Brown and the 20-year-old Tatum both looked like NBA playoff-seasoned vets in Southern Wisconsin on Sunday as they not only rescued the C’s from being blown out but also sparked one of the top comebacks in recent playoff history. Down by 20 points midway through the third, the C’s went on a 12-2 run. A twisting Brown layup in traffic and a Tatum 3-pointer then cut the Bucks lead to nine, 69-60 with 3:13 left in the third.

Brown’s fourth 3-pointer of the day – which came a good three feet behind the 3-point stripe early in the fourth quarter - cut the Bucks lead down to just three, 75-72. A 28-footer by Brown with 1:29 remaining sliced the Milwaukee lead to only one, and then on the very next Celtics possession Tatum’s 17-foot isolation jumper over Khris Middleton at the top of the key with 52.4 seconds left punched the Celtics through the wall. The C’s finally had a lead, 100-99.

In the final two quarters the Celtics, led by Brown and Tatum, had shown a championship-level amount of basketball toughness in the playoffs, and on the road.

“I’ve been around a lot of teams and have been fortunate to be around a lot of really tough teams,” Celtics head coach Brad Stevens said of this 2017-18 group a few weeks back to ESPN. “I’m not sure I’ve been around one that, in the face of a tough stretch on a basketball court, responds better than this one.”

In the final 52.4 seconds of Sunday’s game, however, the Celtics did show that they probably don’t have the horses to win big in the 2017-18 playoffs. Tatum’s iso jumper was the last Celtics field goal of the game, and Milwaukee was the one to make that last big bucket with Giannis Antetokounmpo tipping in a Malcolm Brogdon miss with 5.1 seconds left.

Brown finished with 34 points, having made 5-of-8 from 3-point range and Tatum finished with 21 on 7-of-16 shooting from the floor.

The Celtics do not raise Atlantic Division championship banners from the rafters, nor will they start hanging Indianapolis Colts-style moral victory pennants anytime soon either. But make no mistake, Sunday’s loss to the Bucks was special. It was the day Brown and Tatum became bona fide NBA playoff weapons.